The long term goal of this research is to determine the mechanism by which vitamin E functions in the regulation of differentiation, proliferation and maintenance of the germinal epithelium of the mammalian testis. That alpha-tocopherol has a role in normal testicular differentiation and function has been established in a wide variety of animal species. Polyenoic fatty acids are abundant in testicular tissue and vary in concentration as a function of development and maturation. Vitamin E has a role in the regulation of polyunsaturated fatty acid metabolism and at present our work indicates that the effect of vitamin E may be chiefly on those pathways involved in the turnover of this fatty acid. The immediate objective of the present study is to investigate several of these pathways: a) biosynthesis of docosapentaenoate, b) retroconversion of this fatty acid to arachidonate, and c) the biosynthesis of prostaglandins. These studies will be performed in the testes of the whole animal as well as in subcellular fractions of testicular tissue from both control and vitamin E deficient rats during the course of maturation. Our work has shown that prostaglandins are synthesized in rat testis and that the major types that occur in this tissue, prostaglandin E2 and prostaglandin F2 alpha, are derived from arachidonic acid. Since prostaglandins have regulatory effects in cells and tissues, the hypothesis that there may be a relationship between polyenoic fatty acids, vitamin E, and prostaglandins in the control of testicular function will be investigated.